tesco best
I was wiv Orange Contract for years, then switched to tesco (who use o2's network) and never looked back. Orange Customer service is rubbish, constantly messed up my bills! However, Customer service at tesco is excellent very help friendly staff (they are all manned by o2 staff). Virgin uses Tmobile, but Ive heard on the grapevine that they are re-negotiating their deal with them (because of the coverage and pricing). Other MVNO (Mobile Virtual Network Operators) are BT Mobile (who use vodafone) Carphones talktalk (and the other CPW MVNOs) use Tmobile. Best option IMO is Tesco, or contract on o2. The 3 network use their own 3G services on their network, but when no coverage it uses o2 (and soon it will be Orange instead).